The present invention relates to coffee makers and, more particularly, to a counter-top unit particularly suited for home and other low-volume use.
Counter-top coffee makers are well known in the art. Typically, a coffee maker has a glass or plastic carafe for receiving brewed coffee, the carafe being supported by, or resting upon, a heating element or surface, as seen in U.S. Pat. No. D390,409 to Littman, issued Feb. 10, 1998.
Sometimes a coffee maker includes a thermally insulated carafe for receiving brewed coffee as seen in U.S. Pat. No. 5,463,932 to Olson, issued Nov. 7, 1995; however, a heating element or surface typically is not provided in conjunction with a thermal carafe. The insulated carafe is capable of maintaining the coffee""s temperature absent this additional heat source. The absence of the exposed heating element or surface may be a safer alternative for certain consumers, such as those having small children in the household. Additionally, consumers may transport the insulated carafe containing coffee while maintaining the temperature of the coffee. Unfortunately, consumers must choose between a coffee maker with an uninsulated carafe and a coffee maker with an insulated carafe.
Centrifugal coffee makers are also well known in the art. For example, U.S. Pat. No. 5,265,517 to Gilbert, issued Nov. 30, 1993, discloses a centrifugal coffee maker which heats the water and discharges the water over the coffee grounds through two discharge ports located equidistantly from the axis of rotation. A basket containing the coffee grounds spins as the water is discharged. The water flows through the coffee grounds, out of the centrifugal basket, and is collected in a carafe or container. However, this design creates an annular pattern on the grounds, failing to wet much of the grounds. This is insufficient at best and wasteful at worst.
A second apparatus for making coffee and having a centrifugal brewing system is disclosed in U.S. Pat. No. 1,602,632 to Zorn, issued Oct. 12, 1926. The coffee maker uses a plurality of tubes arranged in a spiral to discharge water over coffee grounds. The water is distributed in a circular pattern onto the grounds despite the more complicated structure, resulting in the same inefficiency and waste.
These prior centrifugal brewing systems have a significant drawback in that often the coffee grounds in the rotating basket are not thoroughly and evenly wetted. This may result in a weaker cup of coffee being produced than was anticipated relative to the amount of grounds added to the machine. As a result, extra grounds may have to be added to create a proper strength cup of coffee, which results in wasted grounds.
A further problem encountered by centrifugal brewing systems is overflow of the grounds from the basket during brewing. As a centrifugal basket spins, the slurry of coffee grounds and water is forced against the sides of the basket from the centrifugal force. If the water is unable to exit the centrifugal basket at a sufficient rate, the slurry mixture may overflow the basket, resulting in coffee grounds becoming mixed with the brewed coffee and, thus, producing a cup of coffee with undesirable sediment. This problem is due, in part, to the high speed at which the basket typically is spun. U.S. Pat. No. 5,265,517 to Gilbert, issued Nov. 30, 1993, discloses a centrifugal basket which preferably spins at 280-350 rpm to force the coffee grounds and water slurry to rise along the interior walls of the centrifugal basket. The coffee escapes through narrow horizontal ports located in the middle portion of the basket walls. The basket intentionally is designed so that the coffee exits the basket slowly to provide sufficient contact time between the grounds and the water; this is believed to be necessary to produce an optimum coffee flavor. To prevent the slurry from overflowing the walls of the basket, the basket is provided with an inwardly-extending rim ring which is snap fit for removal by the user. The ring must be removed to place a coffee filter within the basket.
To heat the brew water prior to depositing it over the coffee grounds, both centrifugal and standard brewing systems use either batch or serial heating. A batch heating system heats all of the brewing water prior to beginning the brewing cycle (i.e. prior to depositing any of the water on the grounds). Batch heating systems include a water heating chamber and a distributor in the bottom of the chamber for regulating the flow of the heated water out of the chamber. The water is stored and heated in the heating chamber until it reaches a specified temperature, usually 195xc2x0-205xc2x0 Fahrenheit. The water is then released through the distributor to flow into the basket containing coffee grounds. The distributor is immersed in water as it rests on the floor of the heating chamber and has water flowing through it. Lime often accumulates on its exterior and within its flow holes, reducing the flow rate of the heated water; thus, the flow of water into the grounds basket is reduced, resulting in a longer brewing time. Ultimately, the distributor may be sufficiently restricted or even blocked so as to require replacement. Often, as a practical matter, this requires replacement of the entire coffee maker unit.
A serial heating system heats the brew water as it flows through a pipe just prior to its being distributed over the coffee grounds. This system includes a water flow pipe and a heating element adjacent to a portion of the flow pipe. The heating element heats the water in the adjacent portion of the flow pipe to at least 212xc2x0 Fahrenheit, vaporizing the water. The water vapor condenses as it continues past the heating element and is deposited into the basket containing coffee grounds. When the coffee maker is initially filled with water, a portion of the water often flows through the flow pipe to a position downstream of the heating element. When the brewing cycle is activated, the portion of water adjacent the heating element is heated and vaporized. The water vapor moves downstream, pushing the portion of unheated water before it, and the unheated water is deposited over the coffee grounds. For optimal coffee flavor, the brew water should be 195xc2x0-205xc2x0 Fahrenheit when it contacts the coffee grounds. Thus, the extraction of the coffee may be adversely affected by having insufficiently heated water used in the brewing process.
The aforementioned problems are overcome by the present invention wherein a coffee maker has interchangeable glass and thermal carafes, a water distribution system that disperses water more uniformly over the coffee grounds, a rotating grounds basket that minimizes overflow of the coffee grounds, and a serial heating system that minimizes the flow of unheated brew water over the grounds. In an alternative embodiment, the coffee maker includes a batch heating system allowing for easy replacement of the distributor.
More specifically in a first aspect of the invention, the coffee maker includes a glass carafe and a thermal carafe, both of which fit interchangeably within the carafe cavity of the coffee maker. The coffee maker further includes a carafe heating element or surface upon which the thermal and glass carafes rest when one of the carafes is in position within the carafe cavity. A sensor or switch on the coffee maker unit senses whether the glass carafe or the thermal carafe is within the cavity. When the glass carafe is within the cavity, the heating surface under the carafe is activated to maintain the temperature of the brewed coffee. When the thermal carafe is sensed within the carafe cavity, the heating surface is not activated.
In a second aspect, the coffee maker includes a serial water heating system that maximizes the amount of brew water that is heated in the desired temperature range of 195xc2x0-205xc2x0 Fahrenheit. The heating system includes a water flow pipe, a portion of which is adjacent to a heating element, and a control system. The heating element is activated by the control system at the beginning of the brew cycle for a short time. The heating element is then deactivated for a short time. This allows the heated portion of the brew water to transfer heat to the unheated brew water downstream of the heating element without causing the downstream water to be dispersed over the coffee grounds. The control system then re-activates the heating element for the remainder of the brewing cycle, causing vaporized and then condensed water to be driven through the system and deposited on the coffee grounds
In a third aspect, the coffee maker includes a showerhead for dispersing the heated brew water over the coffee grounds at a variety of radially distinct locations. As disclosed, the showerhead includes a descending trough, the upper end of which is connected to an outflow end of the water flow pipe. The heated brew water enters the showerhead and flows toward its lower end. The showerhead contains several holes radially spaced above a centrifugal grounds basket. The heated water flows through these holes and is deposited on several discrete radially spaced locations on the coffee grounds contained in the centrifugal basket. As the basket spins, the water is driven by gravity and centrifugal forces through the grounds, thus evenly wetting the grounds. Additionally, the showerhead is easily accessible by a user to manually remove lime accumulation from the trough and holes so that the flow of the brew water is not impeded.
In a fourth aspect of the invention, an improved rotating grounds basket allows for a greater grounds capacity while producing an optimal flavored coffee using relatively low speed centrifugal extraction. At the lowered speed, the grounds and water slurry does not climb the walls of the basket, thus reducing overflow of the slurry. Several relatively large vertical ports are positioned within the basket walls to allow the coffee to easily escape the basket. The ports extend to the bottom of the basket so that the angular velocity need only be sufficient to thoroughly wet the grounds and force the slurry against the lower portion of the basket walls. The radial dispersal of the water by the showerhead over the grounds allows the water to initially contact a large portion of the grounds, thus extracting a maximum of the coffee flavor in a minimal amount of time. Thus, in the improved basket, the slurry need not climb the walls nor exit through small ports to provide sufficient contact time between the water and grounds. The basket is spun relatively slowly, preferably at 100-150 rpm, so that the slurry does not climb the walls, and the slower speed allows for sufficient contact time between the grounds and water prior to the coffee""s exiting the basket through the side ports.
In an alternative embodiment of this invention, the coffee maker may have a batch heating system in which all of the brewing water is heated prior to beginning the brewing process. A water heating chamber holds and heats the brew water, which is then released through a modular distributor positioned on the bottom of the chamber. This modular distributor may be easily removed by hand for cleaning or replacement. This overcomes the need to replace the entire coffee maker.